This invention relates to a fuel injection control device and method for an engine and particularly for a two stroke crankcase compression type of engine.
As is well known, it is the practice to control the individual cylinders of a multi-cylinder engine so that they will operate in substantially the same fashion. As a result of this, both the spark timing and fuel injection timing and duration for each cylinder is set substantially the same and the events for each cylinder are timed in relation to their respective firing order. However, there are running conditions of the engine when the individual cylinders cannot be treated identically to each other.
For example, when the cylinders of a group of cylinders all discharge into a common exhaust system, the exhaust pulses from one cylinder can cause a pressure in the exhaust port of another cylinder that can affect the charging of that other cylinder. Thus, if all cylinders are treated the same, then one cylinder may have performance that is deteriorated from that of another cylinder. Unequal performance between the cylinders gives rise to a substantial loss of performance not only of the one cylinder but of the entire engine.
This problem is particularly acute with two cycle crankcase compression internal combustion engines that have a plurality of cylinders discharging into the same exhaust pipe. As is well known, the exhaust gas pulses from one cylinder can force charge back into another cylinder whose exhaust port is open at the same time so as to increase the residual exhaust gases in that other cylinder. This phenomenon is utilized sometimes to achieve an effect known as "exhaust supercharging". This condition is particularly acute in outboard motor application wherein the length of the exhaust system is substantially restricted due to the compact nature of such devices.
It is, therefore, a principal object of this invention to provide an improved fuel injection system and control therefor for an engine that will insure comparable performance of each cylinder.
It is a further object of this invention to provide a fuel injection system and control for a two cycle crankcase compression engine.
It is a further object on this invention to provide an improved fuel injection system and control method for an outboard motor.